This paper presents the approach for the assessing of the operational reliability of a multi-layer thick-walled tube made of Rubber with textile reinforcement. The analysis of the fatigue accumulation process is carried out within the framework of the concept of the continuum mechanics of damage. The mathematical model, which takes into account the accumulation of damages in case of a random spread of the strength characteristics of the material, as well as the process of stochastic aging for the elastomeric matrix of the composite and possible random variation of the workload has been developed. In this case, the aging process is modelled as a reduction of the endurance limit of the material. In this paper, the mean equivalent strains of the tube and their possible statistical variation in operation have been investigated on the basis of the finite element method. To solve the above problems, a submodeling method has been employed in this work. The probability of non-failure operation of the tube has been determined using the methods and models proposed. The influence of the rate of the aging process on the lifetime of the tube has been estimated.

Bitumen in pure form is not suitable for modern roads and present traffic. This has forced engineers to modify bitumen to improve its performance during service life. Two routes are known for bitumen modification, that is chemical and physical modifications. Therefore, there are chemical and physical modifiers. Among physical modifiers, polymers (thermoplastics, Rubbers and thermosets) are the most interesting ones. Rubbers are very good bitumen modifiers. In this work non-vulcanized Rubbers were incorporated into bitumen. The resulting blends showed better high and intermediate performance compared to the base bitumen. The improved properties are lower penetration and higher softening point. The low temperature properties such as Frass breaking point were not improved. New formulae for estimating bitumen’s performance using the results of conventional Frass and ring and ball tests were introduced. The morphology of the blends, depending on the rheological properties and compatibility of the Rubber with bitumen, was different. Polybutadiene formed a continuous phase mixture in bitumen. This was observed due to the compatibility of this Rubber with bitumen. Due to lesser compatibility between polymer and bitumen, SBRs and natural Rubber formed polymeric inclusion dispersed in bitumen.

Double-pipe heat exchangers are commonly used in various industries, including power plants, solar cells, refineries, and automotive. The double-pipe heat exchanger is one of the most used simple exchangers in the industry. In this study, we employ computational fluid dynamics to investigate the flow characteristics of nanofluids within a double-pipe heat exchanger featuring a square inner tube and a circular outer tube (SC). The simulations are conducted under constant heat flux conditions, exploring laminar and turbulent flow regimes. Numerical results for water flow under forced convection are compared with reference results for validation. The results indicate that as the Reynolds number increases, particularly in turbulent flow regimes, the Nusselt number in nanofluid flow increases more than in water flow. For instance, in the case of aluminum oxide nanofluid flow at a Reynolds number of 500, the Nusselt number demonstrates a nearly 5% enhancement over water flow. In contrast, at a Reynolds number of 20000, this enhancement escalates to approximately 20%. Three types of nanoparticles are considered to investigate the effect of nanoparticle type on heat transfer and pressure drop. The results show that the use of nanoparticles has a slight effect on the friction factor while significantly enhancing heat transfer.

Effect of the blends of different polyethylenes (LDPE=low-density polyethylene, LLDPE=linear low density polyethylene and HDPE=high density polyethylene) and Rubbers (PBR= polybutadine Rubber, SBR=styrene butadiene random copolymer, NR=natural Rubber and SEBS=styrene-ethylene-butylene-styrene block copolymer) on bitumen properties was investigated. PBR-PE blends form a physical network in bitumen medium, whereas their SBR, NR and SEBS counterparts do not. The properties of the resulting bituminous blends are comparable with those of SEBS blends. LLDPE shows a higher rate of effectiveness on bitumen properties as compared with other polyethylenes. SBR blends show a better elastic recovery and film forming properties. Addition of heavy vacuum slops (HVS) oil into the ternary blends of Rubber-PE-Bitumen results in Rubber inclusions volumes. The Rubber swelling increases as HVS oil concentration increases. HVS oil concentration could be adjusted depending on the designed performance grade (PG). SBR-PE blends found to be the most effective blends on bitumen properties.